Should Juventus win their 29th Championship this weekend, they will lift the trophy under a cloud of suspicion.

This week the entire board at the club resigned following the publication of taped telephone conversations between the senior Juventus board members, Luciano Moggi and Antonio Giraudo, and high-ranking Italian football federation (FIGC) officials.

The conversations, part of an inquiry by Turin prosecutors, were recorded during the 2004-2005 season. They appear to show that Mr Moggi was seeking to influence which referees were being sent to officiate at Juventus games.

On several occasions he called Pierluiggi Pairetto, the joint head of the Italian refereeing federation and vice-chairman of Uefa's referees' commission, asking for an official to be changed.

According to one transcript, he was particularly annoyed when the German referee, Herbert Frandel, was chosen to take charge of a Champions League qualifying game between Juve and the Swedish club Djurgarden. Mr Frandel's offence was to disallow a Juve goal.

Mr Moggi later called Mr Pairetto berating him for his choice of referee.

An even more shocking conversation takes place between Mr Pairetto and Paolo Dondarini, the referee selected to officiate Juventus's Serie A match against Sampdoria that season.

"You know what you have to do," Mr Pairetto says.

"Make sure you see everything. Even that which isn't there."

The investigators found no legal basis to proceed against anyone on criminal grounds but they urged the Italian FA to conduct their own inquiry.

The president of the federation, Franco Carraro, was given the transcripts of the telephone conversations in February but failed to take any action.

Mr Carraro quit his post on Monday.

Shares dive

On Friday morning, police searched the federation's offices in Rome as well the offices of the referees association. It was part of their ongoing inquiries, they said.

Juventus need just one point this weekend to lift the Championship trophy but sources close to the club say they are now terrified they could be relegated as a result of the subsequent inquiry.

Shares in Juventus dived on Friday for the second consecutive day. They have lost some 15% of their value since Wednesday's close.

As well as the inquiry into the telephone conversations, Mr Moggi is also being investigated by magistrates in Naples and Rome in two separate inquiries into illegal gambling and the operation of a management company owned by his son, Alessandro.

The GEA management firm has over 200 players and coaches on its books.

Rome magistrates have also put the company under investigation for "illegal competition with use of threats and violence".

'Clean sweep' call

But this investigation goes far beyond Juventus and those connected to the Turin club.

At least 17 Serie A games from last season are being investigated by the federation.

Four of the games involving Juventus were overseen by senior Italian referee Massimo de Santis.

Mr de Santis is one of two Italian referees down for this summer's World Cup.

Mr De Santis met prosecutors in Naples on Wednesday - prosecutors confirmed on Friday he was one of those under investigation.

Senior football managers in Italy have since called for a clean sweep of the football association.

Inter Milan coach Roberto Mancini said: "I won't stay in Italy if the winners of the championship have already been decided before we take the field.

"It wouldn't take much to change things - we need proper rules and honest people. Otherwise we should suspend the championship.